The present invention relates to an optical pickup device for recording information on an optical disc or for reproducing information from an optical disc.
A conventional optical pickup device includes a frame structure mounting a light source, a photodetector, and some other optical elements forming an optical path. Installed on the frame structure is a base section mounting an objective lens and a lens driving system.
When recording information on an optical disc or reproducing information therefrom, a beam light emitted from the light source is directed along the optical path to pass through the objective lens so as to irradiate an information recording surface of an optical disc. Meanwhile, a control means is used to control the movement of the objective lens in both a focus direction and a tracking direction, and a light reflected from the optical disc is also directed to pass through the objective lens so as to be received and detected by the photodetector.
In order to record or reproduce information correctly, the optical pickup device should be adjusted such that an optical axis of the objective lens is arranged on the optical path in a correct manner. For this reason, such optical device is usually provided with a position adjusting means to adjust the optical axis of an objective lens with respect to an information recording surface of an optical disc.
FIG. 9 is a sectional view in side elevation indicating the structure of a position adjusting means provided in a conventional optical pickup device. As shown in FIG. 9, a lens holder 102 on which an objective lens 101 is mounted and fixed, is movably supported by a support section 104 through a plurality of elongate flexible members 103, in a manner such that the objective lens 101 may be driven in both a focus direction (indicated by an arrow F in FIG. 9) and a tracking direction (perpendicular to the paper of FIG. 9). The support section 104 has an integrally formed protruding portion 104a having a partially spherical shape. In detail, the convex portion 104a is engaged in a notched recess 105a of a frame structure 105 carrying a light source (not shown), a photodetector (not shown), and some other optical elements (not shown) forming an optical path.
Referring again to FIG. 9, the support section 104 may be adjusted in its position with respect to the frame structure 105, by driving screws 107 in a clockwise or counterclockwise direction. Then, an adjusted position may be maintained by means of a spring 106 which causes the convex portion 104a to be urged against the notched recess 105a. In fact, there are two screws 107 formed in pair and disposed in two axial directions. By properly adjusting the pair of screws 107, the convex portion 104a may get tightly engaged in the notched recess 105 with the optical center of the objective lens 101 serving as a central axis. Therefore, it is possible to have the optical axis of the objective lens 101 adjusted in a radial direction (tracking direction) and in a tangential direction (indicated by an arrow T in FIG. 9).
However, with the conventional optical pickup device shown in FIG. 9, since the convex portion 104a is formed on the bottom of the base section 104 right under the objective lens 101, a sufficient space is needed in the thickness direction (optical axis direction) of the device. As a result, the optical pickup device has to obtain a considerable thickness, rendering it difficult to produce a compact device. Moreover, since two screws 107 are needed to be disposed in two axial directions for adjusting the optical axis of the objective lens in both the radial direction and the tangential direction, it is difficult to reduce the number of necessary parts for forming the optical pickup device, thus production cost may not be easily lowered.
It is an object of the present invention to provide an improved optical pickup device having a small thickness and capable of adjusting the position of an objective lens using only a simplified structure, so as to solve the above-mentioned problems peculiar to the above-mentioned prior art.
According to the present invention, there is provided an improved optical pickup device holding an objective lens in a manner such that the objective lens is movable in both a focus direction and a tracking direction, said optical pickup device comprising: an optical pickup body; a lens holder for holding the objective lens; a movable support member connected to the lens holder through a plurality of elongated flexible members for movably supporting the lens holder; a support section provided on the optical pickup body, said support section being arranged substantially perpendicular to an optical disc on which information is to be recorded or from which information is to be read out. In particular, the movable support member is adjustably attached on the support section in such a manner that the position of the objective lens is adjustable.
In one aspect of the present invention, the elongated flexible members are linear wires, with one end of each connected to the lens holder and the other end of each to the movable support member, said linear wires being arranged in parallel to the optical disc on which information is to be recorded or from which information is to be read out.
In another aspect of the present invention, the support section is formed with a restricting groove having a predetermined width and extending in a direction substantially perpendicular to the optical disc, the movable support member is provided with a cylindrical sliding pin engageable and slidable in the restricting groove. Further, the support section has a sliding surface for the movable support member to slide thereon, the movable support member may be moved on the sliding surface so that its position is adjusted to thereby adjust the position of the objective lens. In particular, the sliding surface is a concave spherical surface which is formed by a part of a single spherical surface. Alternatively, the sliding surface is formed by combining several flat surfaces.
In further aspect of the present invention, the movable support member is formed with a plurality of spherical projections on one surface thereof which will come into contact with the sliding surface. Particularly, the spherical projections are arranged such that the normal line of each spherical projection at a contacting point with the sliding surface, may generally pass through the optical center of the objective lens.
In still further aspect of the present invention, the position adjustment of the objective lens includes adjusting the optical axis of the objective lens in both a radial direction and a tangential direction, with respect to the information recording surface of an optical disc on which information is to be recorded or from which information is to be read out. The adjustment in the radial direction is performed by rendering the pin to pivot in the restricting groove and rendering the movable support member to move over the sliding surface. The adjustment in the tangential direction is performed by rendering the pin to slide in the restricting groove and rendering the movable support member to move over the sliding surface.
The above objects and features of the present invention will become better understood from the following description with reference to the accompanying drawings.